The guy clearly doesn't know what he's talking about. Take a cheap DAC. Swap out it's crappy power supply with a nice linear one and tell me if you can't hear a difference. If that DAC has a socketed op amp for its output stage, swap out the op amp for a nice discreet one and tell me if you can't hear a difference again.
Is there a lot of snake oil in high-end audio? Of course. But to say that nothing in a DAC matters except the chip is just completely untrue.